It’s going to be a tough year to stay current with influencers.

Under normal circumstances, Influencer50 research puts the attrition among a company’s top 50 influencers at about 20 percent per year. That means that in a 12-month period, 10 of the 50 will have changed jobs.

It doesn’t look as though 2009 will offer normal circumstances. I would expect that rate to climb. Large and mid-sized companies are reducing headcount, and consolidating through mergers and acquisitions. Small businesses and independent contractors may be forced to bridge lean sales by hooking up with larger companies.

It’s a good idea to keep a closer eye on the top 50 influencers in each of your markets. Watch for new voices rising up, established voices tuning out, changes in focus.

Remember too that influence is not necessarily a real-time activity. Decision-makers tend to remember an influencer’s opinion long after obtaining it.